Versioned relational database system with an optimistic constraint model

Abstract

Techniques for doing optimistic constraint checking in a versioned relational database system. The techniques find a subset of the versions of a table that contain all of the rows that need be checked for violation of a constraint when a given version is modified. When the versions of a table are organized into a directed acyclic graph (DAG), the subset for a given version is the ancestry of the given version, that is, the given version plus the ancestors of the given version in the DAG. Within the ancestry, the set of rows that must be checked is termed the version view. A row that belongs to the set has a primary key that is the latest version of the primary key in the given version's ancestry. The technique may be used for constraints including the referential integrity constraint and the unique key constraint. The metadata used to compute the version view is disclosed, as well as the manner in which the constraint checking techniques interact with the workspaces that provide access to the versions. The workspaces may be organized as a DAG. The manner in which the workspaces are organized determines how changes are propagated in the versioned relational database and thus the versions whose ancestry has to be checked for constraint violations.

Description

RELATED APPLICATIONS[0001]The present patent application is a continuation-in-part of U.S. Ser. No. 09 / 557,592, Ramkrishna Chatterjee, et al., System and method for enforcing referential constraints between versioned database tables, filed Apr. 22, 2000, and having the same assignee as the present patent application. U.S. Ser. No. 09 / 557,592 issued June 24, 2003 as U.S. Pat. No. 6,584,476. That patent is further incorporated by reference in its entirety into the present patent application. The portion of the present application which is taken from the parent is in the section titled RIC checking in a VRDBS. The present application is also closely related to U.S. Ser. No. 10 / 205,084. Sanjay Agarwal and Ramkrishna Chatterjee, Versioned database system with multi-parent versions, filed on even date with the present patent application and having the same assignee.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The invention relates to relational database systems generall...

AI Technical Summary

Benefits of technology

[0051]The object of the invention is achieved by a versioned relational database system in which there is a set of versions of a table and metadata which makes it possible to define a proper subset of the versions of the table that includes those versions in which a constraint...

Problems solved by technology

The versioned relational data base system may then use the metadata to locate rows in the versions of the subset for which the operation may result in a violation of a constraint.

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